Gregory Kopiloff, 35, pleaded guilty to one count each of mail fraud, accessing a protected computer without authorization to further fraud, and aggravated identity theft.

As part of a plea agreement, another count of aggravated identity theft was dropped.

Kopiloff acknowledged using file-sharing programs to invade victims' computers to get access to their personal information in tax returns, credit reports, bank statements and student financial aid applications. He then used that information to open credit lines and shop online.

Kopiloff admitted using the personal information of more than 50 people to fraudulently purchase and resell more than $73,000 in merchandise.

Although people have been prosecuted for using networks to illegally share copyright music, movies and software, the Justice Department, after Kopiloff's September arrest, called this its first case against someone accused of using file-sharing to commit identity theft.

According to court documents, Kopiloff used peer to peer file-sharing programs, which are most commonly known for their use in replicating copyright protected music and videos. Using programs such as Limewire, he could search the computers of others who were part of the file-sharing "network" for tax returns and credit reports that had been stored electronically.

He also obtained personal information by more old-fashioned methods, such as stealing mail or taking records from trash cans, the U.S. attorney's office said.

Kopiloff's sentencing was scheduled for Jan. 28 before U.S. District Judge James L. Robart. Mail Fraud is punishable by up to 20 years in prison and a $250,000 fine. Accessing a protected computer carries a maximum penalty of five years in prison and a $250,000 fine. Aggravated identity theft carries a two-year prison sentence, to be served consecutive with the prison time imposed for the underlying conviction.